Techniques have been developed and widely used for remote control of devices installed in automobiles (hereinafter, also referred to as “vehicles”). For example, techniques have been developed for starting engines of vehicles by remote control to preliminarily warm-up the engines, and for activating air conditions of vehicles by remote control to control a temperature in the vehicles after starting the engines before passengers enter the vehicles. Such techniques are disclosed in Japanese Laid-open Patent Publication No. 11-230013 (patent document 1).
Patent document 1 describes a technique involving a control circuit for control of an aftermarket electric device installed in a vehicle. This vehicle has an engine control circuit that is wirelessly controllable to start/stop the engine of the vehicle through operation of a portable controller (remote controller) provided with a start switch and a stop switch. The aftermarket electric device is turned on by an operation-start signal which is an operation signal from the start switch during operation of the engine and turned off by an operation-stop signal which is an operation signal from the stop switch during a halt of the engine.